Submersible pump stage

ABSTRACT

A submersible pump stage comprises an impeller comprising a first front top disc and a first rear top disc, first blades located between the front and the rear top discs, a bushing and a diffuser comprising a second front top disc and a second rear top disc, second blades located between the second front and second rear top discs. The second rear top disc has through holes passing in end surfaces and located circumferentially. A number of the through holes is selected at least equal to a number of interblade channels. The holes are made so as to provide an overflow of a liquid from a front pocket of this stage of the submersible pump into each interblade channel of a preceding stage diffuser.

FIELD OF THE DISCLOSURE

The invention is related to the area of the stages of submersible centrifugal pumps used for pumping liquid media including those containing oil, it may be used for liquid natural deposits' production, including, hydrocarbons from oil wells.

BACKGROUND OF THE DISCLOSURE

There are different designs of stages of centrifugal pumps described, for example, in Certificate of Invention SU 576438, Patents RU 2083880 and SU 125408. A disadvantage of the known designs is absence of constructive elements for protection against accumulation of solid particles in the cavities between rotating and fixed surfaces.

A stage of a centrifugal pump is described in Patent RU 68613. This stage contains an impeller including front and rear top discs, blades located between the front and rear top discs, a bushing and a diffuser including front and rear top discs, and blades located between the front and rear top discs. A disadvantage of this apparatus is that, as solid particles are accumulated in a front pocket, the solid particles begin to significantly increase the friction between the rotating parts of the submersible pump, which may result in the motor damage and results in a very significant impeller top disc wear.

SUMMARY OF THE DISCLOSURE

Stages of a centrifugal or diagonal submersible pump necessarily have negative design peculiarities such as cavities between an impeller front and rear top discs and surfaces of a diffuser which were named front and rear pockets. These design elements are due to the necessity of mating the stage rotating parts (impeller) with fixed (diffuser) as well as with the need to minimize overflows inside the stage. When a pure liquid is pumped through the pump stage the impact of these cavities is not significant, but if a liquid containing solids (like sand or proppant) is supplied to the stage inlet, these cavities begin working as traps for solid particles which penetrate the pockets via gaps between the impeller and the diffuser. Mostly, this negative process is true for the front pocket because to prevent the impeller wedging an upper gap between the top disc and the diffuser casing has the size exceeding the diameter of the solid particles which may be present in the pumped liquid. As the solid particles accumulate in the front pocket they begin to significantly increase the friction between the rotating parts of the submersible pump which may result in the motor damage and leads to a very strong abrasive wear of the impeller disc.

The suggested invention provides for continuous forced flushing of the front pocket to prevent solid particles' accumulation therein which significantly reduces the abrasive wear of the impeller top disc and substantially extends the motor service life.

A stage of a submersible pump stage comprises an impeller including a first front disc and a first rear top disc, first blades, located between the first front and the first rear top discs, a bushing and a diffuser including a second front disc and a second rear top disc, second blades, located between the second front and rear top discs. The second rear top disc of the diffuser has through holes passing in end surfaces and located circumferentially. A number of the through holes is selected at least equal to a number of interblade channels and the through holes are made so as to provide an overflow of a liquid from a front pocket of the stage into each interblade channel of a diffuser of a preceding stage.

In various embodiments, the number of the through holes can be selected divisible by the number of the interblade channels.

In further embodiments, a diameter of each through hole is selected within the range from 1 to 10 mm.

In yet further embodiments, the diameter of each through hole is selected within the range from 2 to 4 mm.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows the view of a submersible pump stage, FIG. 2—a view of a diffuser of the submersible pump stage.

DETAILED DESCRIPTION

A submersible pump stage comprises an impeller 1 and a diffuser 2. The impeller 1 consists of a first front top disc 3 and a first rear top disc 4, first blades 5, and a bushing 6. The diffuser 2 similarly consists of a second front top disc 7 and a second top rear disc 8, second blades 9 and a bushing 10. FIG. 1 also shows the location of “abrasive” holes 11 made in an end surface of the second rear top disc 8 of the diffuser 2 and connecting a cavity defined between a surface of the first front top disc 3 of the diffuser 2 of this stage and a surface of a third rear top disc of a diffuser of a preceding stage. The design and location of the “abrasive” holes in the diffuser are shown in FIG. 2.

To prevent a motor damage it is necessary to provide continuous forced flushing of a front pocket. One of the options to implement the front pocket flushing is making dedicated “abrasive” holes connecting the front pocket of the submersible pump stage with the diffuser preceding stage of the submersible pump. In this case, re-circulating liquid motion occurs in the front pocket which prevents accumulation of solid particles, and the liquid motion via the “abrasive” holes carries away the solid particles from the pocket cavity into the diffuser of the preceding stage, from where the solid particles are routed again to the pump stage inlet. Pumping of the liquid through the “abrasive” holes happens due to a pressure drop between the front pocket of this stage and the diffuser of the preceding stage. The pressure drop value at the “abrasive” holes is nearly equal to a submersible stage head.

The “abrasive” holes are used to reduce abrasive wear of the submersible pump stage because they arrange continuous liquid circulation via the stage front pocket and thus prevent the accumulation of solid particles therein.

These holes 11 are drilled through the end surface of the second rear top disc 8 in such a way that a constant liquid overflow from the front pocket into each interblade channel of the diffuser is provided. The diameter of the holes is selected within the range from 1 to 10 mm, preferable—from 2 to 4 mm, depending on a diameter of the solid particles entering the pump, the size of a top radial gap between the impeller and a casing of the stage and a stage head. To adjust a flow rate of a liquid flushing the submersible stage front pocket the location and number of the holes in the diffuser channel may be varied. 

1. A stage of a submersible pump comprising: an impeller comprising a first front top disc and a first rear top discs, first blades located between the first front top disc and the first rear top disc, a bushing, a diffuser comprising a second front top disc and a second rear top disc, the second blades located between the second front top disc and the second rear top disc, the second rear top disc having through holes passing in end surfaces and located circumferentially, a number of the through holes is at least equal to a number of interblade channels and the through holes are made to provide an overflow of a liquid from a front pocket of this stage of the submersible pump into each interblade channel of a diffuser of a preceding stage of the submersible pump.
 2. The stage of claim 1 wherein the number of the through holes is selected divisible by the number of the interblade channels.
 3. The stage of claim 1 wherein a diameter each through hole is selected within the range 1-10 mm.
 4. The stage of claim 3 wherein the diameter of each through hole is selected within the range 2-4 mm. 